Docosahexaenoic/arachidonic acid omega-hydroxylation system and differentiation in the human colonic adenocarcinoma cell line, Caco-2.
The homogenate from Caco-2 cells of day 13 or 15 after subculturing had high omega-hydroxylation activity of docosahexaenoic acid (22:6(n-3)) or arachidonic acid (20:4(n-6)). Activity, maximal at pH 8.0, was inhibited in the presence of CO or metyrapone and in the absence of NADPH. Omega-hydroxylation activity of lauric acid in the homogenate was not detected. Apparent Michaelis constant (Km) values for 22:6(n-3) and 20:4(n-6) were found to be 4 and 7 microM. Omega-hydroxylation activity considerably increased with growth up to day 13 and then decreased until day 20 even though alkaline phosphatase (ALP) and leucine-aminopeptidase (LAP) activity increased with growth to day 20. Metyrapone in cultures caused omega-hydroxylation, ALP and LAP activity to decrease, while sodium butyrate dose-dependently increased that of omega-hydroxylation, ALP and an endogenous endonuclease and decreased lactate dehydrogenase (LDH) activity in culture medium. The omega-hydroxylation system thus appears quite likely to be associated with cytochrome P450, differentiation and/or apoptosis rather than cytotoxic cell death of Caco-2 cells. Substrate specificity, however, differed from that of human cytochrome P450 4A11.
Yamane
M
M
Department of Biochemistry, Tokyo Medical College, Japan.
Shimizu
S
S
Abe
A
A
Yamane
S
S
D000230:Adenocarcinoma / Q000378:metabolism*; D000469:Alkaline Phosphatase / Q000378:metabolism; D016718:Arachidonic Acid / Q000378:metabolism*; D002087:Butyrates / Q000494:pharmacology; D020148:Butyric Acid; D018938:Caco-2 Cells; D002454:Cell Differentiation; D004281:Docosahexaenoic Acids / Q000378:metabolism*; D006801:Humans; D006900:Hydroxylation; D007931:Leucyl Aminopeptidase / Q000378:metabolism
D002087:Butyrates; D020148:Butyric Acid; D004281:Docosahexaenoic Acids; D016718:Arachidonic Acid; D000469:Alkaline Phosphatase; D007931:Leucyl Aminopeptidase